Generally described, industrial gas turbines and steam turbines may include a casing with an inner shell mounted to an outer shell. The inner shell may hold the shrouds and the nozzles. The inner shell may be split into two or more segments that may be joined or bolted together by flanges and the like to facilitate maintenance and repair. During transient operations, temperature changes in the turbine may produce axial and radial temperature gradients in the turbine shells and elsewhere. These temperature gradients may create large thermal stresses therein. Such stresses may have an impact on overall component lifetime.
For example, the inner turbine shell may be supported by a pair of shell arms. The shell arms support the weight of the inner shell and must accommodate the torque that results from the aerodynamic loads on the nozzle vanes during operation. The failure of a shell support arm could result in a catastrophic failure of the overall gas turbine engine. As such, at least a segment of the inner turbine shell must be replaced if cracks are found. Such repair procedures may be time consuming and costly.
There is thus a desire for an improved turbine casing. Such an improved turbine casing may adapt to thermal stresses and the like. Such a turbine casing may increase low cycle fatigue life for prolonged component operation with little additional costs.